Electronic devices, such as portable media players, storage devices, tablets, netbooks, laptops, desktops, all-in-one computers, cell, media, and smart phones, televisions and other display devices, navigation systems, and other devices have become ubiquitous in recent years. These devices often include an audio jack through which the devices may receive and/or provide audio information. The audio jacks may include, or be connected to, electronic circuitry such as audio drivers for driving headphones or speakers, audio receivers for receiving audio signals from a microphone, and others. The audio jacks may be arranged to receive audio plugs that may be connected through audio cables to other electronic circuits such as home stereos, powered speakers, headphones or headsets, audio receivers, and other circuits.
These audio plugs may be electrical audio plugs. That is, they may include a number of ring-shaped contacts along their lengths. These contacts may connect to conductors in an audio cable attached to the audio plug. Contacts for three-pole audio plugs may include left audio, right audio, and ground. Contacts for four-pole audio plugs may include contacts for left audio, right audio, ground, and microphone.
These four-pole audio plug contacts may be configured in a conventional manner. That is, a tip of the audio plug may be a left audio channel contact, followed by a right audio channel, ground, and microphone contacts.
However, some four-pole audio plugs may be configured in an alternate manner. While the tip and following contacts remain a left audio channel contact and a right audio channel contact, the last two contacts are reversed relative to the conventional audio plug. Specifically, the next contact is a microphone contact, followed by ground.
In each of these configurations, a connection between a contact in an audio jack and a corresponding contact in an audio plug may be resistive. Also, the contacts themselves may be resistive. Return current may flow at the ground contacts. The return current flowing through the contact resistance may generate a voltage. This voltage on ground may generate crosstalk between left and right channels of an audio headset.
Thus, what is needed are circuits, methods, and apparatus for grounding contacts in an audio jack that may reduce this crosstalk.